| 摘要 |
PURPOSE:To detect an abnormal current when an antiparallel short circuit takes place, by combining an overcurrent detecting circuit with an antiparallel short circuit detecting circuit which utilizes a suppression signals for a forward and a backward silicon controlled rectifier converters. CONSTITUTION:An abnormal current detecting circuit 20 comprises an operational resistor, an operational amplifier, a comparator and an OR circuit. The operational amplifier 20-3 inverts the polarity of a current detection signal of a backward silicon controlled rectifier converter 7. As a result, the polarity of an input signal to another operational amplifier 20-7 becomes negative and the simultaneous currents of direct current transformers 6, 7 due to an antiparallel short circuit do not cancel each other. The comparator 20-14 compares the current with an overcurrent detection level to detect an overcurrent. Thus, the abnormal current under the antiparallel short circuit is detected and a trouble is prevented from expanding. |
